Application of Native Bacillus sp. for Sustainable Jhum Agro-ecosystem

Abstract

Bio-inoculants based on native Bacillus spp. have the potential to resuscitate the short fallow Jhum (slash and burn), degraded agro-ecosystem of Northeast India. Plant growth-promoting (PGP) native microbial isolates were investigated for reinvigorating growth of an upland rice variety (Bhalum). Of the 37 distinct bacterial isolates from fields left fallow for 2 years, 27% exhibited two or more PGP traits. Three native isolate strains SH2, MB1 and SS2 were selected as bio-inoculators, based on their levels of indole production, phosphate solubilization, siderophore and HCN production. They also showed no apparent toxicity on the tested rice seeds while enhancing the germination vigor of rice seeds with increased shoot length (39.7%), root length (37%) and plant height (32.7%) when compared to the untreated seeds. Under greenhouse conditions, plants derived from seeds treated with SH2, MB1 and SS2, displayed significant increments and enhanced growth biomass with 39.7% and 37.1% enhancement in shoot and root development versus the control. Phylogenetic analysis based on 16S rRNA sequences characterized SH2, MBI and SS2 as Bacillus luti, B. pacifus, and B. subtilis, respectively. The NCBI GenBank database and the phylogenetic dendrogram generated confirmed their identity with their related type strains. Their robust physiological response to temperature, pH and salt stress will bolster survival in the harsh slash-burn and shifting agriculture cycle. Consequently, application of SH2, MBI and SS2 would maximize growth productivity engendering the eco-restoration, sustainability and resolving low crop productivity of the short fallow Jhum agro-ecosystem